Don't call Jason Derulo Usher.

A guy in Vegas did, and he got knocked out for it.

Watch Derulo jump over two barricades at the Aria hotel and attack a guy who yelled Hey, Usher! F*ck you, bitch!" 

Derulo, who was with a large bodyguard, also hit another man.  Hotel security eventually broke up the fight.

Perhaps Derulo didn't want people to think he's the R&B singer who has herpes and gives it to guys.

We can understand that.